Small, non-coding RNAs (sRNAs) are critical in regulating gene expression in many organisms and, in humans, have been implicated in some types of cancer. In Escherichia coli, numerous sRNAs are expressed in response to environmental stresses and positively or negatively regulate translation and stability of target mRNAs. Synthesis of the global stress regulator, RpoS, in E. coli is stimulated by several sRNAs. Base pairing of the sRNA, DsrA, to rpoS mRNA is predicted to protect the mRNA from degradation and modulate the secondary structure of the mRNA to allow efficient translation. The effects of sRNA base pairing and the roles of specific proteins in the processing and stability of rpoS mRNA will be examined. Regulated expression of wild-type and mutant forms of DsrA and rpoS mRNA will be combined with ribosome binding assays to analyze the role of sRNA pairing in the translation of the mRNA. Genetic screens will be used to identify new cellular factors that facilitate DsrA activity. To understand the physiological role of the novel sRNA, RyhA, in RpoS production, screens for regulators of ryhA expression will be employed and the mode of action of RyhA on RpoS synthesis will be compared to DsrA.